Temperature control thermostatic switch device



Aug. 21, 1951 I v. WEBER ETAL TEMPERATURE CONTROL THERMOSTATIC SWITCHDEVICE 2 Sheets-Sheet 1 Original Filed Feb. 19, 1946 pa R A $2 f H my Mi m I .A mm v wm H T Aug. 21, 1951 v. WEBER ET AL TEMPERATURE CONTROLTHERMOSTATIC SWITCH DEVICE 2 Sheets-Sheet 2 Original Filed Feb. 19, 1946Patented Aug. 21, 1951 TEMPERATURE CONTROL THERMOSTATIC SWITCH DEVICEVictor Weber and William S. Kunzler, Greens burg, Pa., assignors toRobertshaw-Fulton Controls Company, Greensburg, Pa., a corporation ofDelaware Continuation of application Serial No. 648,780, February 19,1946. This application December 27, 1948, Serial No. 67,532

10 Claims.

This invention relates to control devices and, more particularly, tocondition responsive controls for electrically driven apparatus such asclothes dryers. This application is a continuation of our copendingapplication, Serial No. 648,780 filed February 19, 1946 now abandoned.

Appliances of this nature may include a motor driven shell or drum inwhich the clothes are placed and an electrical heating element fromwhich heated air may be circulated by a fan or blower throughout theload of clothing which is undergoing the drying operation. It isapparent that considerable latent heat remains in the load uponcompletion of the drying operation although the heating element has beencutoff. Hence, the load cannot be removed from the appliance with safetyuntil after a cooling-down period which should not be too prolonged.

An object of this invention is to render the control of the clothesdrying operation fully automatic after the starting operation isaccomplished.

Another object of the invention is to ensure a predeterminedcooling-down period before the drying operation is completed.

Another object of the invention is to further dry the load of clothingduring the cooling-down period.

Another object of the invention is to eliminate the possibility ofdamage to the clothing should the appliance become unattended afterbeing started.

Another object of the invention is to require a manual resettingoperation to again place the appliance in full operation after aninitial heating cycle.

Other objects and advantages will become apparent from the followingdescription taken in connection with the accompanying drawings, wherein:

Fig. 1 is a front elevation of the heat control device;

Fig. 2 is a side elevation with-portions of the cover of the devicebroken away to show the inside structure;

Fig. 3 is a front elevation similar to Fig. 1 but with the front coverremoved;

Fig. 4 is a rear elevation of the device with the rear cover removed;

Fig. 5 is a side elevation similar to Fig. 2 but showing other detailsof construction;

Fig. 6 is a. partial enlarged section taken on the line V'I-VI of Fig.3;

Fig. 7 is a section taken on the line VII-VI of Fig. 1; and

2 Fig. 8 is a wiring diagram. Referring more particularly to thedrawings, a main housing for the heat control structure comprises anL-shaped frame It to which is secured by the screws I2 a channel-shapedcover I4. The arrangement provides a housing having an open end withinwhich a block I6 of insulating material is securedby means of the screwsI8. As shown in Fig. 5, the frame I 0 is adapted to be fastened to anaccessible portion of the appliance (not shown) by means of the lugs 20through which suitable securing means may project.

The cover I4 is provided with a centrally located boss 22 having anaxial opening in which a spud-piece 24 is secured and projects outwardlyof the cover I4. Journalled on the spud-piece 24 is a bushing 26carrying a handle 28 having a dial 3B thereon. The dial 30 carriesindicia representing the various heatingpositions together with an offpositionall of which cooperate with a stationary reference point 32formed on an escutcheon plate 34 which surrounds the dial 30 and issecured to the cover I4 by a bracket 36.

The handle 28 is non-rotatably mounted on the bushing 26 by cooperationwith a cam element 38 which, as shown more clearly in Fig. 5, is formedon the bushing 26 intermediate the ends thereof. The handle 28 isprovided with a recess 40 on the inner face thereof which interlockswith the cam element 38 to prevent relative rotation between the handleand the bushing. The cam element 38 is adapted for engagement with anoperating bar 42 upon rotation of the handle 28 to off position. The bar42 projects from the interior of the cover I4 through the boss 22thereon and is slidably supported adjacent the cam element 38 by aportion of the bracket 36. The cam element 38 is provided with a steppedportion 44 with which the operating bar 42 is adapted for engagement toprevent further rotation of the handle 28 in a.clockwise directionbeyond the off position. The operating bar 42 is normally urgedoutwardly of the cover I4 by a leaf spring 46 secured to the front wallof the cover I4 and extending. through a slot formed in the operatingbar 42 as shown in Fig. 5.

The spud-piece 24 also carries a threaded element or stud 48 having adetentj'50 projecting laterally from one end and. cooperating with aslot 52 formed in the bushing 26 to prevent rela-' tive rotation. Theinner end of the stud 48 supports an expansible and contractiblediaphragm 5.4 and serves to move the diaphragm relative to the cover I4upon rotation of the handle 28. The interior of the diaphragm 54 is incommunication with a capillary tube 56 which is partly coiled in- .sidethe boss 22 and extends therefrom exterior ,provided in the bulb 60 andthe capillary tube 56 so that upon expansion of the liquid as a resultof the heat to which the bulb is subjected the liquid will be forcedthrough the tube into the expansible and contractible diaphragm therebyactuating it to a sufficient extent to operate parts now to bedescribed.

A button 62 provided on the face of the diaphragm 54 opposite the stud48 abuts a depression formed in a main actuating lever 64. This lever,which is generally of U-shaped conformation, is provided with aknife-edge 66 serving to connect the legs of the U-shaped lever andwhich is seated in a knife-edged bearing 68 formed on a bracketlOsecured to the inner wall of the L- shaped frame I0. The base of themain actuating lever 04 is recessed at the center portion to provide aseat for one end of a tension spring 12, the other end of which ishooked in an aperture formed in the center cross bar 14 of an R-shapedcontrol lever 16.

, The two legs 18 and 80 of the control lever iii are provided withknife edges cooperating with spaced knife-edged bearings 32 formed in achannel-shaped support 84 extending substantially parallel with the baseof the frame I0. As shown more clearly in Fig. 6, the support 84 carriesproiections 86 which are loosely mounted in the wall of the L-shapedframe I adjacent the base thereof and serve to retain the sup ort inposition at one end thereof. Lateral displacement of the control lever16 is prevented by a bracket 90 carried by the inner wall of the frameI0 and having arms projecting on each side of the legs I8 and 80. The suport 84 also carries at the front end an adjusting screw 88 which may beadjusted to raise or lower the support 04 and change the tension of thespring I2 as desired.

An .inverted V-shaped take-up arm 92 is attached to the control lever I6rearwardly thereof by means of forwardly projecting spaced lugs 94suitably notched for engagement with oppositely dis osed shoulders 96formed on the le s I8 and 80 of the control lever 16. The take-up arm 92is further provided at the o posite end with a hook 98 which extendsaround the underside of the cross-bar of the R-shaped control lever I6at the central portion thereof. The hook 98 limits the movement of thetake-u arm 92 with res ect to the control lever I6 and cooperates withthe lugs 94 to attach it thereto.

The, take-up arm 92 extends laterally bevond the cross-bar of thecontrol lever 16 and carries a contact block I00 of insulating materialmounted thereon-for restricted pivotal movement in a horizontal plane. Acontact bridge I02 is secured to the rear face of the contact block I00for cooperation with contacts I04. I06 mounted on the insulating blockI6 and pro ecting exteriorly of the cover I 4. It will be observed thatin this embodiment the contact I04 is provided with terminal connectionsincluding the screw I08 while the contact I06 is adapted for permanentconnection with a conductor I I0. It will be apparent. however, thatsuch arrangement can be modified as dictated by the circuit arrangementwith which the control apparatus is used.

The structure so far described constitutes a snap action mechanism bymeans of which the control lever I6 can effect contact operation. Thus,as the liquid in the bulb 60 and the capillary tube 56 expands inresponse to temperatures prevailing at the oint where the bulb islocated, the diaphragm 54 will also expand and urge the free end ofthemain actuating lever 04 toward the knife-edged bearing 62 of thecontrol lever I0. Due to tension of the spring .12, the control lever I6and its companion take-up arm 92 will be moved to the right as viewed inFig. 2 with a snap action as the actuating lever 64 moves overcenterpast a line between the respective bearings of the two levers. Such snapaction causes engagement of the contact bridge I02 and the contacts I04,I06, as will be apparent.

The closed position of the contacts I02, I04 and I06 will continueuntilthe diaphragm 54 starts to contract upon cooling of the bulb 60'whereupon a similar over center snap action will occur but intheopposite direction to cause contact disengagement'as the contact lever"I6 resumes its normal position as shown in Fig. 2. Separation ofthelevers 64 and "I6 under bias of the spring I2 is prevented by a limitstop member I09 which is secured to the insulating block I 6 and extendsinto the path of movement of the lever I6.

Additional contacts are provided for support by the insulating block I6and are located to one side of the contacts I04, I06. These contacts maybe two in number and are designated H2 and H4, respectively. Theconductor H0 connects contact I06 with contact II2 permanently, whilecontact I I4 is similar to contact I08 in having a terminal connectionincluding a screw II6. The contacts I4, I06 which, as stated, oooperatewith the contact bridge I02 are also provided with back contacts H8 andI20, respectively. The back contacts II8, I20 and the contacts H2, H4cooperate'with a pair of contact bridges I22, 524, respectively.

The contact bridges I22, I24 are mounted upon separate insulating platesI26 carried by flexible members I28 upon the opposite bifurcated ends ofa secondary lever I30. The secondary lever I30 extends between the armsof the bracket and is provided with lateral projections I32 pivotallymounted in the arms 90 and serving to support the secondary lever andassociated parts in condition for pivotal movement to engage anddisengage the contact bridges I22 and I24. A compression spring I34 ismounted between the secondary lever I30 and the inner wall of the frameI 0 on the side of the pivotal mounting opposite the contact bridgesI22, I24, thus serving to bias the contact bridges out of engagementwith the contacts IIB, I20, and H2, H4, respectively.

The secondary lever I30 is adapted to be operated during the snap actionof the main actuating lever 64. Thus, interengaging means on the mainlever 64 and the secondary lever I30 are provided andtake'the form' of arocker I36 mounted on a' pivot I38 supported on the depending portion ofan angular arm I40 projecting from the bracket 90 immediately below andinwardly of one of the arms thereof. The rocker I36 extends toward themain actuating lever 64 in position to be engaged thereby when overcenter-snap action occurs. Preferably, the rocker I36 has a ramp I 42formed thereon and the lever 64 is provided with a lateral projectionI44 which will ride along the ramp I42 and serve to. tilt the rocker I36during the over center snap action of the lever 64.

In order to maintain the contact bridges I22, I24 in engagement withtheir respective contacts, the bias of the spring I34 is overcome by alatching arrangement now to be described. The underside of the rockerI36 is engaged by the free end of a U-shaped strip of spring metal I46which is secured to the channel-shaped support 84 and has its free endspaced therefrom. The opposite end of the rocker I36 is thus urged.about the pivot I38 toward a projection I48 which is formed on adepressed portion of the secondary lever I 30. Latching engagementbetween the secondary lever I30 and the rocker I36 is secured by formingthe end of the rocker adjacent the projection I48 with a notch I56 withwhich the projection I48 may engage. As shown in Figs. 2 and 6, thesecondary lever I30 is in what may be termed the unlatched position,notch I50 being disengaged from the projection I48. In this position,the spring I34 has biased the secondary lever I30 from normal latchedposition so that the contact bridges I 22, I24 are disengaged from theirrespective contacts. A button I52 is provided on the exterior of thecover I4 to reciprocate a pin I54 carried by and extendin into operativeengagement with the secondary lever I30 when the button I52 isdepressed. The pin is normally biased out of engagement with the leverI30 by a compression sprin I56 operative between the button and thecover I4. The pin I54 engages the lever I30 on the side thereof oppositethe projection I48 and thus serves to pivot the lever against the biasof the lever spring I 34.

Secured to the back of the L-shaped frame I0 is a housing I58 ofinsulating material. A pair of oppositely disposed screws I60 xtendingbetween the frame I0 and the housing I58 serve to secure these partstogether. The housing I58 carries on one side thereof a pair of fixedcontacts I62, I64 with which a movable contact bridge I66 is adapted tocooperate. The contact I64 is in the nature of a permanent connectioninasmuch as a conductor I68 is permanently connected at one end thereto.The contact I62, however, is provided with terminal connections includinthe screw I10.

The contact bridge I66 is carried by a switch arm I12 of insulatingmaterial which is pivoted by a mounting I13 on a frame I14 secured bymeans of the screw I16 to the housing I 58. A coil spring I18 operativebetween a projection I19 on the frame I14 and the switch arm. I12 servesto bias the latter and therefore the contact bridge I66 carried therebyinto engagement with the contacts I62 and I64. Disengagement of thesecontacts I62, I 64 with the contact bridge I65 is effected by a pin I80which extends from the mounting I 13 through alined apertures in thehousing I58 and the frame I0 for engagement by the adjacent insulatingplate I26 which is carried by the secondary lever I30. It is apparentthat contact bridge I66 is either disengaged or engaged with itscontacts simultaneously with the disengagement or engagement of contactbridges I22, I 24 with their contacts.

The other portion of the housing I58 is provided with a pair of flexibleswitch arms I82, :84 carrying contacts I86, I88, respectively at theirfree ends. The switch arms I 82, I84 are secured at the opposite ends tothe housing I 58 by screws I90 and are provided with separate terminalcon- 6 nections I92. The contacts I86, I88 are adapted to cooperate withcontacts I94, I96, respectively, which are secured to the housing I58 byscrews I91. The conductor I68 is connected at its oppo-v .tends from thebase of the housing I58 inter-- mediate the switch arms I82, I84 andserves as a pivot point for one end of an actuating plate 202 ofinsulating material which underlies the switch arms I82, I84. The otherend of the plate 202 is suported on the end face of a hollow projection204 which carries a pin 206 adapted for free reciprocation therein. Thepin 206 extends through suitable alined apertures in the wall of thehousin !58 and frame I0 for engagement by the end of the operating bar42 as shown clearly in Fig. 7. The arrangement is such that uponlongitudinal movement of the operatin bar 42 in a right-hand directionas viewed in Fig. '1, the pin 206 will move the plate 202 and serve todisengage the contacts I86, I88 from their related fixed contacts A I94,I96.

Referring now more particularly to the wiring diagram shown in Fig. 8,it will be apparent that the pair of terminals I 92 may be connected byline wires 203, respectively, to a source of electrical energy such as ahouse current supply. A heating element A has one end connected by awire 2I0 to the terminal l1! and the opposite end connected to one endof a second heating element B which has its opposite end connected by awire 2I2 to the terminal I IS. A ground wire 2 I 3 is tapped into theconnection between the heating elements A and B.

Heat distributing means in the form of an electric motor-operated fan orblower (not shown) is provided for circulating heated air throughv theload of clothing which is placed in the drying drum (not shown) to bedried. The motor may also operate the drum which revolves during thedrying operation. The motor is shown in Fig. 8 as having one terminalconnected to ground and the opposite terminal connected by a conductor2I4 to the terminal I68. Further description of circuits for the heatingelements and the motor will be given in connection with the descriptionof the operation of the device, which follows.

In the operation of the device it may be assumed that the dial 30 is inthe ofi position so that the cam element 36 has forced the operating*bar 42 inwardly to engage and move the pin 206 and thus operate theflexible switch arms I 82, I84 to disengage the contacts I86, I88thereon from the contacts I94, I96, respectively. Thus, the current isbroken on both sides of the line and movement of the handle 26 in acounter-clockwise phragm 54 and the button 52 to the right but isinsufficient to operate the main actuating lever: 64 and cause snapaction or the control lever 16.

Thus, the auxiliary switching means for the motor comprising the contactbridge I02 remains in position where the contacts I04, I06 aredisengaged. However, the operating bar 42 no longer causes disengagementof contacts I86, I88 from contacts I94, I96, respectively. The buttonI52 is then operated to cause the pin I54 to engage and move the lowerend of the secondary lever I30, thus overcoming the bias of the springI34 and permitting the spring arm I46 to tilt the rocker I36 and engagenotch I50 with projection I48. The secondary lever I30 is thus latchedin its forward position with the contact bridges I22 and I24 inengagement with the contacts II8, I and H2, H4, respectively. Due to theforward movement of the secondary lever I30 the contact bridge I66 issimultaneously moved by the contact arm I12 under bias of the springI'I8 into engagement with the contacts I62, I64 as previously explained.

A circuit may now be traced on Fig. 8 from the right-hand line wire 208,terminal I92, contacts I88, I96, wire I68, contact I62, contact bridgeI66, contact I64, wire 2I0, heating element A, heating element B, wire2I2, contact II4, contact bridge I24, contact II2, wire I98, contactI94, contact I86, terminal I92 and left-hand line wire 208. The circuitfor both the heating elements is thus complete.

At the same time, a circuit for the motor may also be traced by way of aleft-hand line wire 208, terminal I92, contact I86, contact I94, wireI98, contact II2, wire III), contact I20, contact bridge I 22, contactH8 and wire 2I4 to one terminal of the motor which, as stated, has itsother terminal grounded. Thus, the circuit for the motor is completedand operation of both the heating element and the motor can occur.

When the temperature in the drying appliance reaches that which has beenpreselected on the dial, then the control will operate thermostatically.That is, the diaphragm 54 will expand sufficiently to cause theovercenter snap-action of the control lever "I6. It should be noted atthis point that the control device can be adjusted so that upon a risein temperature at the bulb 60 the auxiliary switching means for themotor comprising contacts I04, I06 and contact bridge I62 become engagedjust below the preselected setting. However, as long as such contactengagement occurs substantially simultaneously with the disengagement ofthe other contacts due to the snapaction the operation of the motor willnot be interrupted.

Thus, upon snap action of the control lever I6 the projection I44 on themain actuating lever 64 tilts the rocker I36 and releases the secondarylever I30. The contact bridges I22 and I24 carried by this lever I30 arethereby disengaged from their related contacts simultaneously withdisengagement of contact bridge I66 from its related contacts I62, I64by operation of the pin I80. The heating elements A and B are thereforedeenergized but the circuit to the motor is continued through theauxiliary switching means comprising contact bridge I02 and contactsI84, I06.

When the temperature at the bulb 60 drops an amount corresponding to thedifferential of the thermostat then the diaphragm 54 contractssufficiently to cause overcenter snap-action in the opposite direction.The auxiliary switching means is therefore opened by the biasing meanstherefor comprising the spring I2 and the motor ceases to run.

It is thus apparent that the auxiliary switching means comprisingcontact bridge I02 and contacts I04, I06 is operated thermostaticallyand will beopened and closed according to the temperature at the bulb60. The switches controlled by the secondary lever I30, that is, contactbridges I22, I24 and I66 and associated contacts are operatedthermostatically to open position but require manual resetting to closedposition. Thus the heating elements remain deenergized until the controlis manually operated.

It is further apparent that the motor will continue to run and willdrive the fan and drum after the heating elements are cut out until thetemperature at the bulb has dropped to a safe level. Thus, the clothescan then be handled without fear of burning the hands and at the sametime an additional drying period is obtained.

The control is fully automatic. After the wet clothes are put in theappliance and the controls set as described, then the heating cycle andcooling down period will take place and thereafter the appliance willshut itself down. Thus, the appliance will operate safely with noattention on the part of the operator once the controls have properlybeen set. Cross reference is made to copending application of Weber andGarner, Serial No. 688,582, filed August 5, 1946.

It will be understood that various changes may be made in the details ofconstruction and arrangement of parts and that th control device may beutilized for useful purposes other than clothes drying controls. Thepush button control could be omitted and a sliding dial utilized inplace thereof. The rotating motion of the dial could be used asdescribed for settin the tempera- P ture and axial motion for bringingthe switches into contact engaged position. This and other modificationsmay be made within the scope of the appended claims without departingfrom the spirit of the invention.

We claim:

1. A control device comprising switching means having open and closedpositions for controlling an energizing circuit, switching means havingopen and closed positions for controlling a second energizing circuit,means for closing both said switching means to establish said circuits,auxiliary switching means having open and closed positions forcontrolling one of said circuits independently of said switching meanstherefor, means responsive to changes in a condition to be controlled,means for opening both said switching means upon a change in saidcondition affecting said condition responsive means and forsubstantially simultaneously closing said auxiliary switching means tomaintain said one of said circuits, and means for opening said auxiliaryswitching means to discontinue said one of said circuits upon a furtherchange in said condition affecting said condition responsive means.

2. A control device comprising switching means having open and closedpositions for controlling an energizing circuit, switching means havingopen and closed positions for controlling a second energizing circuit,manually operable means for closing both said switching means toestablish said circuits, auxiliary switching means having open andclosed positions for controlling the first said circuit independently ofsaid switching means therefor, means responsive to a condition to becontrolled, means for opening both said switching means upon a change insaid con dition affecting said condition responsive means auxiliaryswitching means to maintain said first circuit, and means for openingsaid auxiliary switching means to discontinue said first circuit upon afurther change in said .condition affecting said condition responsivemeans.

3. A control device forelectrical heat distributing apparatus comprisingswitching means having open and closed positions for controlling aheating circuit, switching means having open and closed positions forcontrolling a heat distributing circuit, means for closing both saidswitching means to establish said circuits, auxiliary switching meanshaving open and closed positions for controlling said heat distributingcircuit independently of said switching means therefor, temperatureresponsive 'IIlEflI'lSy-JTIGHJIS for opening both said switching meansupon a change in temperature aifecting said temperature responsive meansand for substantially simultaneously closing said auxiliary switchingmeans to maintain said heat distributing circuit, and means for openingsaid auxiliary switching means to discontinue said heat distributingcircuit upon a further change in temperature affecting said temperatureresponsive means.

4. A control device for electrical heat distributing apparatuscomprising switching means having open and closed positions forcontrolling a heating circuit, switching means having open closedpositions for controlling a heat distributing circuit, manually operablemeans for closing both said switching means to establish said circuits,auxiliary switching means having open and closed positions forcontrolling said heat distributing circuit independently of saidswitching means therefor, temperature responsive means, means foropening both said switching means upon a rise in temperature aiiectingsaid temperature responsive means and for substantially simultaneouslyclosing said auxiliary switching means to maintain said heatdistributing circuit, k

and means for opening said auxiliary switching means to discontinue saidheat distributing circuit upon a further drop in temperature afiectingsaid temperature responsive means.

5. A control device for electrical heat distributing apparatuscomprising switching means having open and closed positions forcontrolling a heating circuit, switching means having open and closedpositions for controlling a heat distributing circuit, means for biasingboth said switching means to open position, means for overcoming saidbiasing means and closing both said switching means to establish saidcircuits, means for latching both said switching means in closedposition, auxiliary switching means having open and closed positions forcontrolling said heat distributing circuit, means for biasing saidauxiliary switching means to open position, temperature responsivemeans, and means for releasing said latching means to open both saidswitching means upon a change in temperature affecting said temperatureresponsive means and for substantially simultaneously overcoming thebiasing means for said auxiliary switching means for closing'the same tomaintain said heat distributing circuit, said auxiliary switching meansbeing opened by the biasing means therefor upon afurther change intemperature afiecting said temperature responsive means.

6. A control device for electrical heat distributing apparatuscomprising switching means having open and closed positions forcontrolling a heating circuit, switching means having open and closedpositions for controlling a heat distributing circuit, temperatureresponsive means adjustable to different temperature settings, adjllS'Ge ing means for said temperature responsive means including areciprocable element for closi both said switching means to establishsaid circuits, auxiliary switching means having open and closedpositions for controlling said heat distributing circuit independentlyof said switching means therefor, means for opening both said switchingmeans upon a change in temperature affecting said temperature responsivemeans and for substantially simultaneously closing said auxiliaryswitching means to maintain said heat distributing circuit, and meansfor opening said auxiliary switching fians .to discontinue said heatdistributing circuit upon a further change in temperature affecting saidtemperature responsive means.

7. A control device for electrical heat distributing apparatuscomprising switching means having open and closed positions forcontrolling a heating circuit, switching means having open and closedpositions for controlling a heat distributing circuit, means for biasingboth said switching means to open position, temperature responsive meansadjustable to difierent temperature settings, adjusting means for saidtemperature responsive means including reciprocable and rotatable means,said reciprocable means being operative for overcoming said biasingmeans and closing both said switching means to establish said circuits,means for latching both said switching means in closed position,auxiliary switching means having open and closed positions forcontrolling said heat distributing circuit, means for biasing saidauxiliary switching means to open position, said position beingestablished when said rotatable means is adjusted to a selectedtemperature setting, means for releasing said latching means to openboth said switching means upon a change in temperature aiTecting saidtemperature responsive means and for substantially simultaneouslyovercoming the biasing means for said auxiliary switching means forclosing the same to maintain said heat distributingcircuit, saidauxiliary switching mean being opened by the biasing means therefor upona further change in temperature affecting said temperature responsivemeans.

8. A heat control device for an electrical heating appliance having aheating element and a motor, comprising temperature responsive means forcontrolling operating temperatures in the heating appliance, switchingmeans common to both the heating element and the motor and having openand closed positions for controlling separate heating and motorcircuits, adjusting means for said temperature responsive means,manually operable means for closing said switching means andestablishingsaid circuits, means for returning said manually operablemeans to an inoperative position, auxiliary switching means having openand closed positions for controlling said motor circuit, means foropening said switching means upon a change in temperature affecting saidtemperature responsive means and for substantially simultaneouslyclosing said auxiliary switching means to maintain said motor circuit,and means for opening said auxiliary switching means to discontinue saidmotor circuit upon a further change in temperature affecting saidtemperature responsive means, said switching means and. said auxiliaryswitching means remaining open irrespective of subsequent temperaturechanges affecting said temperature responsive means until said manuallyoperable means is operated from said inoperative position,

9. A control device for drying apparatus having an electrical heatingelement and an electric motor, comprising switching means forcontrolling energization of the motor and the current supply to theheating element, auxiliary switching means for controlling energizationof the motor, and temperature responsive means for opening the firstsaid switching means at a predetermined temperature caused by operationof the heating element and simultaneously closing said auxiliaryswitching means.

10. A control device as claimed in claim 9 wherein said temperatureresponsive means is 12 adapted to open said auxiliary switching means inresponse to a temperature drop below sai predetermined temperature.VICTOR WEBER. WILLIAM S. KUNZLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Cobb Apr. 19, 1949

